An RF power amplifier is a type of electronic amplifier that converts a low-power RF signal into a higher power signal. RF power amplifiers are typically used to drive the antenna of a transmitter. Product manufacturers often have a need to control output power from RF power amplifiers. This allows them to optimize performances such as transmission range and battery life and at the same time not to violate government regulations dealing with power emissions. For that purpose, power amplifiers known in the art are usually based on methods that control gate or base drive, adjust bias current or parallel devices together performing power control.
Nevertheless, existing power amplifier control techniques are sensitive to temperature, manufacturing process tolerances and power supply voltage variations. Furthermore, it is difficult to have a linear power control of the output power and to achieve output power steps of 0.5 dB or smaller.